Abstract
Photoconductive field sampling enables petahertz-domain optoelectronic applications that advance our understanding of light-matter interaction. Despite the growing importance of ultrafast photoconductive measurements, a rigorous model for connecting the microscopic electron dynamics to the macroscopic external signal is lacking. This has caused conflicting interpretations about the origin of macroscopic currents. Here, we present systematic experimental studies on the signal formation in gas-phase photoconductive sampling. Our theoretical model, based on the Ramo–Shockley-theorem, overcomes the previously introduced artificial separation into dipole and current contributions. Extensive numerical particle-in-cell-type simulations permit a quantitative comparison with experimental results and help to identify the roles of electron-neutral scattering and mean-field charge interactions. The results show that the heuristic models utilized so far are valid only in a limited range and are affected by macroscopic effects. Our approach can aid in the design of more sensitive and more efficient photoconductive devices.
Highlights
Photoconductive field sampling enables petahertz-domain optoelectronic applications that advance our understanding of light-matter interaction
The same concepts have been applied in air for the measurement of the CEP12 and electric field[13,14], offering additional advantages: they are easier to use since they eliminate the requirement of sample fabrication and inherently use a refreshable target
We present a rigorous theoretical approach based on the Ramo–Shockley theorem, which avoids the artificial separation into photocurrent and dipole contributions and overcomes the limitations of the existing heuristic models
Summary
Photoconductive field sampling enables petahertz-domain optoelectronic applications that advance our understanding of light-matter interaction. In this case, a rather constant current over pressure is expected as depicted as red line, since the total charge scales linearly with pressure, while the mean-free path scales inversely, keeping the dipole strength constant While these heuristic models have been invoked in the interpretation of previous results[13,14,21], their validity has been debated and they failed to provide quantitative predictions. Our extensive numerical particle-in-cell (PIC)-type simulations based on this model enable a quantitative comparison with the experimental results, and enable identifying the roles of electron-neutral scattering and mean-field charge interactions, thereby providing a fundamental understanding of photoconductive sampling of optical fields. The ability of the model for quantitative predictions paves the way toward the implementation of more sensitive and more efficient petahertz optoelectronic devices
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